In the fastening of metallic members, rivets are still popular due to their fastening strength. In the aircraft industry the rivet is widely used for fastening aircraft skin sections to the aircraft frame. As the utilization of robotics increases in the aircraft industry, it is becoming more common to deliver rivets over a relatively long distance from a supply to a rivet holder adjacent a robotic arm.
It has been found that, when the ratio of rivet length to diameter approaches unity, the rivet is likely to tumble as it traverses a delivery path. The problem which this poses relates to the change in orientation of a rivet, after tumbling, so that the rivet may not be in a proper position at the delivery end of the delivery path. An obvious solution is to provide a rivet with a longer length so as to minimize the likelihood of tumbling. However, the thickness of the material through which the rivet must pass determines the assembly length of the rivet and this cannot be altered to achieve the anti-tumbling effect.